Electrochemical machining (ECM) has established itself as one of the major alternatives to conventional methods for machining hard materials and complex contours without the residual stresses and tool wear. ECM has extensive application in automotive, petroleum, aerospace, textile, medical and electronic industries. Studies on Material Removal Rate (MRR) are of utmost importance in ECM, since it is one of the determining factors in the process decisions. So the aim of present work is to investigate the MRR, overcut diameter and overcut depth of AISI P20 work piece by using a rotating copper U-tube tool. Four parameters were chosen as process variables: Feed rate, Voltage, Electrolyte concentration and Tool diameter. The results of experiment show the material removal increase with increasing the feed, voltage and electrolyte concentration but decreases with increasing the tool diameter, and for both overcut diameter and overcut depth they increases with increasing feed ,voltage and electrode diameter but decreases with increasing electrolyte concentration. Grey relation grade (GRD) was also applied to identify the optimal parameter setting in the experiment.